A vehicle, which is driven on a highway, usually travels at a high speed that exceeds 100 km/hour. Thus, when the vehicle continuously travels because the driver of the vehicle does not recognize that an accident has occurred ahead, it is highly possible that a secondary collision occurs in which the vehicle rear-ends a stopped accident vehicle.
In particular, the view is less clear in a very foggy day or at night. Thus, in some cases, even if the traveling speed is reduced after recognizing that the accident vehicle has occurred ahead, it may be difficult to avoid a second collision due to the increase of the braking distance when the traveling speed of the vehicle is high.
In addition, even in the day time when the view is clear, a secondary collision may be caused on a curved road or the like because it is difficult to determine an accident situation.
Due to the reasons described above, very big accidents, such as chain collisions involving ten or more vehicles, have frequently occurred on highways. However, no means for preventing such a chain collision has been provided up to now.
Further, while a vehicle travels on a highway, a delayed or congested section may suddenly occur in a specific zone. Even without an accident situation, a collision accident may occur when the view is less clear because it may not be recognized that there is a delayed or congested section.
When traveling at a high speed on a highway, a driver may feel sleepy due to the monotony of traveling. According to official statistics, 75% of vehicle drivers who travel on a highway feel sleepy within 90 minutes after starting driving. This is because the drivers are in a state in which the ability to recognize the peripheral situation is reduced compared to the usual condition. As a sign of sleepiness, the ability to recognize the speed of the forward vehicle is reduced even though the drivers do not fall asleep.
When a vehicle, which has traveled in a smoothly flowing section, suddenly encounters a delayed or congested section, it may rear end a forward vehicle by failing to reduce the speed.
Even in a case where a traffic accident has occurred similarly to this, secondary accidents may occur in which the rearward vehicles rear end the accident vehicle because the rearward vehicles travel without recognizing the fact that the traffic accident has occurred ahead, but the accident vehicle remains in the stopped state on the road due to the traffic accident.
In consideration of the problems described above, Korean Patent Laid-Open Publication No. 10-2012-0114591 in the name of the applicant of the present application (published on Oct. 17, 2012) discloses a technology in which a camera is installed on a street lamp to determine whether a congestion or an accident occurs, and when it is determined that an accident occurs, a warning is given to the rearward vehicles by causing street lamps therearound to flicker.
Such a configuration is useful for a method of determining a situation of a road and propagating the situation. However, what is demanded in the market is a method that is inexpensive and efficient as compared to a method of causing all the street lamps to flicker.
In addition, because the determination as to whether an accident occurs is made based on an image captured by a camera installed on the road, there is a possibility that an error occurs in determining the accident. Further, because it is difficult to determine an exceptional situation other than an obvious accident, such as temporal stopping according to a driver's poor health or the like, it is demanded to implement a system that is capable of coping with various situations.